The Environmental Determinants of Diabetes in the Young (TEDDY) study was initiated in 2003 by six clinical centers in the United States and Europe, including ours, to identify infectious agents, dietary factors, or other environmental exposures that may trigger or protect against the development of islet autoimmunity and type 1 diabetes (T1D). Additional long-term scientific goals include assessment of potential gene-environment interactions affecting development of islet autoimmunity or T1D, gaining insight on mechanisms, and sharing collected specimens with broader scientific community for studies of T1D pathogenesis and prevention. A total of 424,788 newborns have been screened by HLA-DR, DQ genotyping to identify children at increased risk for T1D and 8677 are followed four times a year until 4 years of age and twice a year thereafter until age 15. Our Clinical Center has enrolled 1834 TEDDY participants; of those 114 have developed persistent confirmed islet autoantibodies and 36 have been diagnosed with T1D, as of 6/30/2012.